The pitch was learned out of desperation, as a last-ditch attempt to salvage a career that was heading nowhere.
For the Dodgers, who had their lead in the National League West trimmed to a mere 3 1/2 games three days earlier, the victory was their third in a row.
For the 25-year-old Haeger (1-1), who was called up from triple-A Albuquerque 11 days earlier, the victory was his first in the major leagues in three years -- and probably earned him another turn in the rotation.
"I'm sure we're going to see him out there," Manager Joe Torre said.
Less clear were the long-term implications of what Torre said was a situation-specific tactical move, summoning All-Star closer Jonathan Broxton from the bullpen in the eighth inning and handing over the ninth-inning role to setup man George Sherrill.
Sherrill closed for Baltimore until he was acquired by the Dodgers on July 30.
Torre said he called in Broxton at that stage because the heart of the Cubs' lineup was due up.
Inheriting a man on first from Haeger, Broxton struck out two in an inning in which the only hit charged to him was a fly ball to right field by Derrek Lee that Matt Kemp lost in the sun and turned into a double.
Of leaving the game in Broxton's hands, Haeger said, "It had to look like 98. He was throwing 98 after I threw 70."
Closing for the first time since he did so for Baltimore on July 12, Sherrill earned his first save as a Dodger.
That was enough to make the home runs hit by Kemp and Casey Blake stand.
The home runs -- Kemp's was in the second inning and Blake's was in the fourth -- were two of only three hits given up by Ted Lilly, who tossed six otherwise solid innings.
But Haeger was better, striking out seven and giving up three hits.
Haeger was also better than he was five days earlier, when he held St. Louis to three runs over seven innings, only to be charged with a loss.
"We certainly haven't given him a lot to work with," Torre said. "Everyone's who's come out of that bullpen or started has to be pretty much bulletproof because we've been struggling scoring runs."
Haeger said his knuckleball moved more than it did in his last start, something that resulted in a lack of command early. Receiving Haeger's pitches once again was backup catcher Brad Ausmus.
"It's an inning-by-inning kind of pitch," Haeger said. "It's such an unpredictable pitch."
The Dodgers infielders felt the same way.
"If he's not sure, we ain't sure," second baseman Orlando Hudson said.
Haeger wasn't sure where his knuckleball would take him when he learned the pitch.
Drafted by the Chicago White Sox in 2001, Haeger figured his career was over after two rough seasons in rookie ball. He left the game for a year, enrolling at Madonna University and walking onto the golf team.
But he wanted back in baseball. The knuckleball gave him another chance.
"I don't want to say it was a desperation move, but it was almost a desperation move," said Haeger, who was encouraged to learn the pitch by minor league pitching coach Chris Sinocori.
Two and a half years later, he was in the majors.
His mother watched him make his first major league start for the White Sox in 2006.
That was the last time she saw him pitch.
VS. CHICAGO CUBS
When: 1 p.m.
Where: Dodger Stadium.
On the air: TV: Prime Ticket, FS West; Radio: 790, 930.
Update: FS West will air the Dodgers' first Spanish-language telecast, offering a visual platform for the broadcasting team of Jaime Jarrin, Pepe Yniguez and Fernando Valenzuela. Billingsley missed a turn in the rotation because of a strained left hamstring but returned Tuesday from an 11-day absence to beat St. Louis. Dempster recently recovered from a fractured toe. He has pitched four times since his return.
-- Dylan Hernandez